| 摘要 |
<p>PROBLEM TO BE SOLVED: To control the sensitivity of a heat ray sensor as a whole in accordance with the ambient temperature. SOLUTION: Four pyroelectric elements 10 to 13 are arranged at regular intervals so that the polarities of the elements 10 to 13 can alternately change and the elements 10 and 11 can be connected in series and output one synthesized signal, and then, the elements 12 and 13 can be connected in series and output one synthesized signal. A controller 19 fetches the ambient temperature from a temperature detecting element 18 and sets the threshold to be given to compactors 15 and 17 in accordance with the ambient temperature. In the case where the ambient temperature is close to the temperature of human beings, the controller 19 discriminates that a heat ray sensor detects a human being when a pulse signal is outputted from one of the compactors 15 and 17. On the other case where the ambient temperature is largely different from the temperature of human beings, the controller 19 discriminates that the sensor detects the human being only when pulse signals are outputted from both comparators 15 and 17.</p> |
